In recent years, the HDMI has prevailed as a communication interface under which a digital video signal, that is, a non-compressed (baseband) video signal (hereinafter, referred to as image data), and a digital audio signal accompanying the video signal (hereinafter, referred to as audio data) are transmitted from, for example, a digital versatile disc (DVD) recorder, a set-top box, or any another audiovisual (AV) source to a television receiver, a projector, or any another display (refer to, for example, a patent document 1).
Between pieces of equipment interconnected under the HDMI, control is implemented under the consumer electronics control (CEC) standard stipulated in the HDMI. However, the CEC standard succeeds a data structure and a transmission speed defined for equipment control through a SCART (syndicat des constructeurs d'appareils radiorecepteurs et televiseurs) terminal in an analog mode. Therefore the transmission speed for control information is as low as approximately 400 bps, and the data structure is defined to basically support transmission in units of 16 bytes. The transmission speed and data structure are therefore unsuitable for control that requires a high-speed response or transmission of control information whose length exceeds 16 bytes.
In a patent document 2, a proposal is made of a technology in which when a received partial transport stream (TS) is outputted from a transmission unit to another video equipment or device, message information alone is separated and extracted, converted into a universal plug and play (UPnP) representation, and then outputted from the transmission unit. In a patent document 3, a proposal is made of equipment in which: data and control information are transferred between a receiving device and a recording device; and the receiving device side includes a processing means which deals with recording control.    Patent document 1: JP-A-2006-319503    Patent document 2: JP-A-2006-319573    Patent document 3: JP-A-2003-209775